Unicondylar Knee Instrument System

ABSTRACT

The present invention provides for an apparatus for cutting a tibia, a stylus, an apparatus for cutting a femur, an apparatus for aligning a femoral cutting guide, and an ankle clamp in support of a unicondylar knee surgery. The present invention further provides for a method of preparing a femoral condyle of a femur for the implantation of a unicondylar femoral knee implant. The apparatus for cutting a tibia includes a unicondylar tibial resection guide that is adjustably connectable to a unicondylar tibial alignment guide and configured to operate concurrently with the tibial alignment guide. The apparatus for cutting a femur includes a spacer block and a cutting guide configured to operate concurrently with the spacer block.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Provisional Application No.60/672,211 filed Apr. 18, 2005, the disclosure of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to orthopedic surgical instrumentation.In particular, the present invention is related to a unicondylar kneeinstrument system and a method of preparing a distal femur for theimplantation of a unicondylar femoral implant.

2. Description of the Related Art

Orthopedic knee implant systems have been used for many years to treatpatients with knee joints that have been damaged by trauma or disease,such as osteoarthritis, rheumatoid arthritis, and avascular neurosis. Aknee arthroplasty resects, cuts, or resurfaces the damaged sections ofthe knee and replaces them with a prosthetic implant.

Most knee implant systems are tricompartmental implants and the surgicalprocedure used with tricompartmental implants is commonly known as totalknee arthroplasty. These implants are known as tricompartmental implantsbecause they are used when the femur is prepared to receive an implantby resurfacing or resecting the three compartments of the distal femur,i.e., the medial and lateral condyles and the trochlear groove.Regardless of the type of implant used, all arthroplasties require thebone to be specifically prepared to receive a corresponding implant byresecting, resurfacing, or deforming the bone to accept the implant.

Minimally invasive surgery (“MIS”) has become of great interest withinthe field of orthopedics. Thus, unicondylar or unicompartmental kneeimplants have become of great interest in the orthopedic industry due totheir small size and applicability to MIS surgical approaches.Unicondylar knee implants are designed to replace only a single condyle(e.g., the medial or lateral condyle) of the distal femur.

Minimally invasive knee surgery has not yet been fully defined. However,minimally invasive knee surgery has generally been considered to includea smaller incision. A typical incision length for a total kneereplacement can be up to 10 to 12 inches long. The general theory behindMIS is that with a smaller incision length, the patient will be able torecover from surgery faster.

Generally, the clinical outcomes for unicondylar knee implants havevaried. Studies have reported long term survival rates for unicondylarimplants to be less than that of comparable total knee implants. Oneparticular cause for such discrepancies is due to the surgical techniqueassociated with implanting the implant.

The unicompartmental implant most widely reported on is the Oxfordimplant. The Oxford implant is a mobile bearing unicompartmental implantthat is implanted with a free-hand technique, i.e., where the boneresections are not guided by instrumentation. Thus, the clinicaloutcomes for these implants have in part been associated with aparticular surgeon's ability in implanting the device. Accordingly, asurgeon proficient in this technique is more likely to have a bettersurgical outcome compared to a less experienced surgeon who is lesstechnically proficient with the surgical technique for implanting theimplant.

Recent advancements in unicondylar knee implants and instruments haveresulted in instrumented techniques for implantation. U.S. Pat. No.6,554,838 to McGovern et al. discloses a unicondylar knee implant thatuses a guided burring technique to implant the femoral component.However, conventional instrumentation systems are bulky and are requiredto be operated from various angles as opposed to a single orientation.Such instrument designs are also not completely conducive to minimallyinvasive surgical approaches or a reproducible surgical result.

Thus, there is a need for a unicompartmental knee instrument system thataddresses the above mentioned deficiencies in current instrument designswhile simultaneously being suitable for minimally invasive surgicaltechniques.

BRIEF SUMMARY OF THE INVENTION

The present invention provides for an apparatus for cutting a tibia insupport of a unicondylar knee surgery that includes a unicondylar tibialalignment guide having a tibia anchor and a unicondylar tibial resectionguide adjustably connectable to the unicondylar tibial alignment guideand configured to operate concurrently with the unicondylar tibialalignment guide that includes, an extended arm having at least onecutting guide surface, and a tibial resection guide base connected tothe extended arm. The apparatus can further include an extended arm suchthat the extended arm is the only element of the unicondylar tibialresection guide within a wound area and wherein the unicondylar tibialresection guide is adjustable in three degrees of freedom. The threedegrees of freedom are heaving, pitching, and rolling. In addition, theapparatus can be configured with an overall thickness of the extendedarm to be about 1 to about 100 mm thick and preferably about 2 to about5 mm thick. Moreover, the unicondylar tibial alignment guides includesat least two telescoping sections and a screw clamp connected to thetibial resection guide base attaching the unicondylar tibial resectionguide to the unicondylar tibial alignment guide.

The present invention also provides for a tibial stylus for use insupport of a unicondylar knee surgery that includes a tibial styluspointer, a member having an open top surface, and a tibial stylus base.The tibial stylus base has a posterior end configured to slidinglyengage along the open top surface and an elongated anterior endconnectable to the tibial stylus configured such that the tibial styluspointer moves along the anterior end of the tibial stylus base. Themember can be a unicondylar tibial resection guide having an extendedarm having at least one cutting surface and a tibial resection guidebase connected to the extended arm. The posterior end of the tibialstylus base can be U-shaped.

The present invention also provides for an apparatus for cutting a femurin support of a unicondylar knee surgery including an instrument handleassembly having an elongated handle having a base and a spacer blockremovably connectable to the base, and a unicondylar resection guideremovably connectable to the base and configured to operate concurrentlywith the space block. The unicondylar resection guide has at least onechannel for guiding a cutting tool and at least one opening forreceiving a fixing element. The unicondylar resection guide can also beconfigured to be slidingly and removeable connectable to the base.Moreover, the spacer block and unicondylar resection guide can beconfigured to operate independently of each other.

The present invention further provides for an apparatus for aligning aunicondylar femoral cutting guide for use in support of a unicondylarknee surgery that includes an instrument handle assembly having a baseand an alignment rod holder connected to the instrument handle assemblythat slides substantially in the medial and lateral direction. Thisapparatus can further include a unicondylar resection guide removablyconnectable to the base or a unicondylar resection guide slidingly andremoveably connectable to the base or a spacer block removablyconnectable to the base. The alignment rod holder includes a firstalignment rod holder base having at least one substantially verticalpassage, a second alignment rod holder base having at least onesubstantially vertical passage, and at least one dowel connecting thefirst and second alignment rod holder bases such that the first andsecond alignment rod holder bases slide within the instrument handleassembly in a substantially medial and lateral direction.

The present invention also provides for an ankle clamp for supporting anapparatus for cutting a tibia in support of a unicondylar knee surgerythat includes an ankle clamp base that includes a pair of base arms,each having a slot, a pair of clamping arms, each having a slot andpivotably connected to the pair of base arms, and a pair of springs,each respectively connecting the base arm and the clamping arm such thatan opening force is provided to open the clamping arms. The pair ofsprings can also be configured to provide a clamping force to close theclamping arms. The pair of springs is connected to a pair of dowelsrespectively, offset a predetermined distance from the pivotableconnection of the clamping arms and base arms. The ankle clamp canfurther include a unicondylar tibial alignment guide connected to theankle clamp base.

The present invention further provides for a method of preparing afemoral condyle of a femur for the implantation of a unicondylar femoralknee implant which includes the steps of, resecting a tibia, determininga least affected site, wherein the site is a distal femoral condyle or aposterior femoral condyle, positioning the knee such that the leastaffected site faces the tibia, positioning a spacer block between theresected tibia and the least affected site, determining an overallthickness for balancing the knee and resecting the femur to a thicknessof a corresponding unicondylar femoral implant, determining a spacerblock and unicondylar femoral cutting block combination that equals theoverall thickness when the knee is in extension, and resecting thedistal femoral condyle.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawings, wherein:

FIG. 1 is a perspective view of an embodiment of a unicondylar tibialalignment guide assembled to a unicondylar tibial resection guide of thepresent invention;

FIG. 2 is a perspective view of an ankle clamp of the unicondylar tibialalignment guide of FIG. 1;

FIG. 3 is a perspective view of the ankle clamp of FIG. 2 in the openposition;

FIG. 4 is a perspective view of section 4 of FIG. 1 of the unicondylartibial alignment guide assembled to the unicondylar tibial resectionguide of FIG. 1;

FIG. 5 is a perspective view of an embodiment of a tibial stylusassembled to the unicondylar tibial resection guide of FIG. 1;

FIG. 6 is a perspective view of the unicondylar tibial resection guideof FIG. 1;

FIG. 7 is a perspective view of an embodiment of a knee joint instrumenthandle assembly of the present invention with an exploded view of aspacer block and base assembly;

FIG. 8 is a perspective view of an embodiment of a unicondylar femoraldistal resection guide of the present invention;

FIG. 9 is a perspective view of an embodiment of a series of spacerblocks of the present invention;

FIG. 10 is perspective view of an embodiment of a series of unicondylarfemoral distal resection guides of the present invention;

FIG. 11 a is an anterior view of a knee joint at full extension with adamaged distal condyle surface and resected tibia;

FIG. 11 b is a side view of a knee joint at 90 degrees of flexion with aresected tibia;

FIG. 12 a is an anterior view of a knee joint at full extension with aresected tibia;

FIG. 12 b is a side view of knee joint at 90 degrees of flexion with adamaged posterior condyle surface and resected tibia;

FIG. 13 is a perspective view of an embodiment of a unicondylar femoralposterior resection guide of the present invention;

FIG. 14 is a perspective view of a series of unicondylar femoralposterior resection guides of the present invention;

FIG. 15 is a perspective view of an embodiment of a unicondylar femoralchamfer and peg-hole guide of the present invention;

FIG. 16 is a perspective view of a series of femoral chamfer and peghole guides of the present invention; and

FIG. 17 is a flowchart of a method for preparing a femoral condyle forthe implantation of a unicondylar knee implant.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the following definitional terms apply. The term“unicondylar” is synonymous with “unicompartmental.” “Anterior” and“posterior” mean nearer to the front or the back of the bodyrespectively. “Proximal” and “distal” mean nearer and farther from thecenter of the body respectively. “Medial” and “lateral” mean nearer orfarther from the median plane respectively. The median plane is animaginary, vertical plane that divides the body into a right and lefthalf. The coronal plane is an imaginary, vertical plane that divides thebody into a front half and a back half. “Superior” and “inferior” meanabove or below respectively. For example, the distal femur has medialand lateral condyles that are superior to the proximal tibia. “Sagittal”means a side profile. Varus means turned inward and valgus means turnedoutward or away from the body. The terms “resection guide”, “cuttingguide”, “resection block”, and “cutting block” are used synonymously.

The present unicondylar knee instrument system can be used forimplanting a unicondylar knee prosthesis in either the medial or lateralcondyle of the left or right knee.

FIG. 1 illustrates an embodiment of a unicondylar tibial alignment guide100 assembled to a unicondylar tibial resection guide 200. Theunicondylar tibial alignment guide 100 can be provided with an ankleclamp 102, a connecting rod 104, a bottom sliding section 112, a middlesliding section 110, a top sliding section 114, a pivoting tibia anchor118, a varus/valgus clamp 122, a flexion/extension clamp 124, a middleslide clamp 126, and a top slide clamp 128. The bottom sliding section112 can be configured with a metatarsal pointer 106. The unicondylartibial resection guide 200 attaches to the top sliding section 114 asshown. The unicondylar tibial resection guide 200 is adjustablyconnectable to the unicondylar tibial alignment guide 100 and configuredto operate concurrently with the unicondylar tibial alignment guide 100.

The ankle clamp 102 may be attached to an ankle by spring loaded arms,elastic straps, extension springs, or other like devices known in theart. The ankle clamp 102 has a varus/valgus clamp 122 about which aconnecting rod 104 slides in a substantially medial/lateral direction.

As further detailed in FIG. 2, the ankle clamp 102 includes an ankleclamp base 10, a pair of base arms 12 a, 12 b, a pair of clamping arms20 a, 20 b and a pair of springs 18 a, 18 b connected to the base arms12 a, 12 b and the pair of clamping arms 20 a, 20 b. The base arms 12 a,12 b each has a slot or opening 14 a, 14 b (not shown) for a spring topass through. At one end of the slot, for example 14 a, is connected adowel 16 a upon which one end of the spring 18 a is attached. The otherend of the slot 14 a is connected to the clamping arm 20 a by a pair ofpins 22 a, 22 b such that the clamping arm 20 a pivots about the pins 22a, 22 b. The opposing end of the spring 18 a is connected to a dowel 24a that is offset a certain distance from the pins 22 a, 22 b along theclamping arm 20 a having a slot or opening 26 a for the spring 18 a topass through. The opposing base arm 12 b, clamping arm 20 b, and spring18 b are configured in the same manner as base arm 12 a, clamping arm 20a, and spring 18 a. The slots 14 a, 14 b & 26 a, 26 b of the base armsand clamping arms along with the offset dowels 24 a, 24 b allow theclamping arms 20 a, 20 b to toggle about pins 22 a, 22 b & 22 c, 22 d asa result of springs 18 a, 18 b.

The springs 18 a, 18 b connect the clamping arms 20 a, 20 b to the ankleclamp base 10 such that the springs constantly provides a force to openthe clamping arms 20 a, 20 b. In addition, the springs 18 a, 18 b canalso be configured to provide a clamping force to close the clampingarms 20 a, 20 b around the ankle of a patient. It is understood that theankle clamp 102 can clamp over the patient's ankle that is completelycovered by soft tissue as well as surgical wrap. The present ankle clampembodiment advantageously allows the instrument to be easily cleaned andsteam sterilized as a result of its design.

FIG. 3 illustrates the position of the clamping arms 20 a, 20 b in theopen position. The connection between the ankle clamp base arms 12 a, 12b and the springs 18 a, 18 b can be configured to allow the clampingarms 20 a, 20 b to remain open when the ankle clamp 102 is in the openposition. The ankle clamp design advantageously allows the user totoggle the ankle clamp from the open to close position and easilyassemble the ankle clamp to the patient without the use of manual forceto keep the clamp open during assembly to the patient. However, thepresent unicondylar tibial alignment guide embodiment can also be usedwith any conventional ankle clamp. Additional suitable ankle clampdesigns are discussed in U.S. Pat. No. 5,197,944 to Steele, which ishereby incorporated by reference in its entirety.

Referring back to FIG. 1, the main shaft of the unicondylar tibialalignment guide 100 includes three sections, a top sliding section 114,a middle sliding section 110, and a bottom sliding section 112. The topand middle sliding sections 114, 110 slide into the bottom slidingsection 112 in a telescoping-like manner. The bottom sliding section 112has a middle slide clamp 126 that fixes or locks-in the position of themiddle sliding section 110 relative to the bottom sliding section 112.The middle sliding section 110 has a top slide clamp 128 that fixes theposition of the top sliding section 114 in a fixed position relative tothe middle sliding section 110. The shape of the sliding sections can beof any suitable shape that allows one section to slide against or intoanother section. In the present embodiment, the middle slide clamp 126can be positioned at the superior end of the bottom sliding section 112.The middle slide clamp 126 has a knob 130 for engaging a screw (notshown) and a casing 132 rigidly fixed to the bottom sliding section 112.The bottom sliding section 112 can be configured to have an I-shapedshaft. The middle sliding section 110 can be configured to have anelongated U-shape that slides against the inset region formed by theI-shaped shaft of the bottom sliding section 112. The top of the middlesliding section 110 can have a corresponding top slide clamp 128,similar to the middle slide clamp 126, about which the top slidingsection 114 slides against. The top sliding section 114 can beconfigured to have an elongated rectangular shape and a curved topsection 116. The top sliding section 114 can also be configured with ascale 134 for measuring the depth of a tibia resection as furtherdescribed below and illustrated in FIG. 4. The unicondylar tibialalignment guide 100 can alternatively be configured with more than twotelescoping sections.

Attached to the end of the curved top section 116 can be a pivotingtibia anchor 118 as shown in FIG. 4. The pivoting tibia anchor 118 hasopenings 120 a, 120 b, and 120 c (not shown) that allows for a fixingelement such as a fixation pin (not shown) to secure the tibia anchor118 to a tibia bone. The orientation of the openings 120 a-c variesdepending upon the pivot of the tibia anchor 118. The pivoting tibiaanchor can alternatively be configured to have any reasonable number ofpassages to allow for additional fixation pins to be used.

Referring back to FIG. 1 the bottom sliding section 112 can beconfigured with a metatarsal pointer 106 at its most distal end. Thebottom portion of the bottom sliding section 112 also has asubstantially horizontal passage 108 that allows for the connecting rod104 to slide in a substantially anterior/posterior direction. Theposition of the connecting rod 104 sliding about the horizontal passage108 can be fixed in position by the flexion/extension clamp 124, similarto that of the middle slide clamp 126.

The connecting rod 104 connects the ankle clamp 102 and the bottomsliding section 112. The connecting rod 104 can be shaped to have twosubstantially orthogonal sliding ends 104 a, 104 b.

FIG. 5 illustrates an embodiment of a tibial stylus 300 slidinglyengaged with the unicondylar tibial resection guide 200. The tibialstylus 300 has a tibial stylus base 302 and a tibial stylus pointer 308.The tibial stylus base 302 can have an elongated base end 304 and aU-shaped connector end 306 for slidingly engaging the extended arm 202of the unicondylar tibial resection guide 200. The tibial stylus pointer308 can be shaped as shown in FIG. 5. The tibial stylus pointer 308 hasa base member 310 and a tibial stylus point 314. The base member 310 hasan opening 312 to allow the tibial stylus pointer 308 to slide along thelength of the elongated base end 304 of the tibial stylus base 302. Theposition of the tibial stylus point 314 can be configured to be at about0 mm above the surface of the unicondylar tibial resection guide cuttingguide surface 204.

The tibial stylus base 302 engages the unicondylar tibial resectionguide 200 by sliding engagement of the U-shaped connector end 306 alongthe open top surface of the extended arm 202 of the unicondylar tibialresection guide 200. The tibial stylus 300 is free to moveanteriorly/posteriorly, medially/laterally, or to rotate internally andexternally when assembled. The tibial stylus point 314 slides freelyalong the tibial stylus base 302. The overall assembly allows for thetip of tibial stylus point 314 to freely move along the entire surfaceof a proximal tibia.

In an alternative embodiment the tibial stylus can be configured as asingle piece construct having a tibial stylus point and a magnetizedbase member. The base member therefore can be magnetically fixed to thecutting surface of the tibial resection guide. Thus, the tibial stylus,while semi-rigidly fixed to the surface of the tibial resection guide,can move freely along the plane of the unicondylar tibial resectionguide, advantageously allowing the tibial stylus point to move freelyalong the entire surface of a proximal tibia.

In yet another embodiment, a tibial stylus can be configured for slidingengagement of the tibial stylus base along a top surface of a member.The member can be a cutting guide, flange, or any other structureconfigured to support the tibial stylus.

In operation, the unicondylar tibia resection guide 200 can be assembledto the top sliding section 114 as shown in FIG. 1. The unicondylartibial resection guide 200 can be configured to slide proximally anddistally along the top sliding section 114 of the unicondylar tibiaalignment guide 100. Proximal and distal positioning can be fixed by useof the tibial resection guide locking screw clamp 210. The tibial stylus300 can then be assembled to the unicondylar tibia resection guide 200as shown in FIG. 5.

With the unicondylar tibia resection guide 200 and unicondylar tibiaalignment guide 100 positioned against the anterior aspect of the knee,the tibial stylus point 314 is positioned on the proximal surface of thetibia, such as the sulcus, to indicate a zero reference point. The topsliding section 114 is then repositioned such that the unicondylar tibiaresection guide 200 is set to the zero mark position 136 located on thescale 134 of the top sliding section 114. The unicondylar tibialresection guide 200 can be then secured to the unicondylar tibialalignment guide 100 and the pivoting tibia anchor 118 pinned (viaopening 120 a) to the proximal tibia by fixation pins (not shown) toprovide a tibia reference point. After the unicondylar tibial resectionguide 200 is fixed in position, the tibial stylus 300 can be removed.The unicondylar tibia alignment guide 100 however can advantageouslyremain in place for the distal and posterior resections, allowing theflexion space to be easily adjusted relative to the extension space byincreasing or decreasing the tibia slope, if necessary, and allowing forthe tibial resection to be made with the unicondylar tibial alignmentguide 100 in position. Thus, overall alignment can be improved since thetibial resection can be simultaneously made with the unicondylar tibialalignment guide 100 in place.

An advantage of the present embodiment is that it allows for the user toeasily adjust resection levels compared to commercial tibial resectionsystems which typically only allow for limited adjust means. The presentembodiment also allows for ease in repositioning fixation pins or foradding additional fixation pins. In addition, the present embodimentallows for the tibial resection guide to be adjustable in three degreesof freedom, moving up and down (heaving), tilting up and down(pitching), and tilting side to side (rolling).

The length of the tibia alignment guide can be adjusted by extending orretracting the middle sliding section 110 and by extending or retractingthe top sliding section 114. Having at least two telescoping sectionsallows for a greater range of length adjustment to accommodate forlarger or smaller patients. Once the correct length is achieved thelength adjustments can be locked in position by securing the middleslide clamp 126 and the top slide clamp 128.

The unicondylar tibia alignment guide 100 is free to rotate in avarus/valgus orientation about the pivoting tibial anchor (via afixation pin through opening 120 a) when the varus/valgus clamp 122 isnot secured. Varus/valgus alignment can be accomplished by aligning themetatarsal pointer 106 with the second metatarsal bone and also byaligning the vertical axes of the metatarsal pointer 106, middle slidingsection 110, and top sliding section 114 with the vertical axis of thetibia. Once varus/valgus alignment is achieved varus/valgus rotation canbe fixed in position by securing the varus/valgus clamp 122.Varus/valgus constraint can be further enhanced by a second or thirdfixation pin (not shown) through additional passages or openings in thepivoting tibia anchor 118.

The unicondylar tibia alignment guide 100 is free to rotate in aflexion/extension orientation about the pivoting tibia anchor 118 whenthe flexion/extension clamp 124 is not tightened. Flexion/extensionalignment can be achieved by referencing tibial slope. Accordingly, theunicondylar tibia alignment guide 100 can be rotated in theflexion/extension orientation until the cutting guide surface 204 of theunicondylar tibial resection guide 200 is parallel with the tibialslope. Once flexion/extension alignment is achieved flexion/extensionrotation can be fixed by securing the flexion/extension clamp 124.

FIG. 6 illustrates an embodiment of a unicondylar tibial resection guide200. The unicondylar tibial resection guide 200 includes an extended arm202 having a cutting guide surface 204, a tibial resection guide base206, and a tibial resection guide locking screw 210.

The extended arm 202 of the unicondylar tibial resection guide 200 has aplanar cutting guide surface 204 that guides a cutting instrument suchas a surgical saw blade. The posterior aspect of the extended arm 202can be contoured to match the profile of an anterior tibial bonesurface. The extended arm 202 can be connected to the tibial resectionguide base 206. The extended arm 202 and the tibial resection guide base206 can be a modular design or of a single piece design. The tibialresection guide base 206 has a substantially vertical passage 208 thatallows for the guide base 206 to be assembled with the unicondylartibial alignment guide 100. The locking screw 210 can be positionedorthogonally to the passage 208 to secure the unicondylar tibialresection guide 200 to the unicondylar tibial alignment guide 100 asshown in FIG. 4. An advantage of the present unicondylar tibialresection guide 200 embodiment is that the extended arm 202 having thecutting guide surface 204 can be made to any needed thickness. Theoverall thickness of the extended arm can be about 1 to about 100 mm orpreferably about 2 to about 5 mm. Alternatively, the unicondylar tibialresection guide 200 can be configured with multiple cutting guidesurfaces.

FIG. 7 illustrates an embodiment of a knee joint instrument handleassembly 400. As shown in FIG. 7, the instrument handle assembly 400includes an elongated handle 402, a base 406, and a spacer block 408.The elongated handle 402 can be curved downward to allow greaterclearance for cutting instruments during use. The base 406 has a pair ofslide tracks 404 a and 404 b (not shown). The spacer block 408 attachesto the base 406. In the present embodiment, the spacer block 408attaches to the base 406 via magnetic attraction i.e., magnets. However,other similar mechanisms known in the art, such as ball plungers,detents, spring connectors, screws, snaps, and temporary epoxy, can alsobe used. The elongated handle 402 can also be configured to have twoopenings 410 a, 410 b for attaching an alignment rod holder 500.

The alignment rod holder 500 has two dowels 502 a, 502 b that passthrough the two openings 410 a, 410 b in the alignment rod handle 402.The dowels 502 a, 502 b are connected to a first and second alignmentrod holder base 504 a, 504 b having two dowel openings 506 a, 506 b. Thealignment rod holder 500 can alternatively be configured with a singledowel and a single dowel opening. In the present embodiment, thealignment rod holder 500 can be configured to have four substantiallyvertical passages or openings 508 a, 508 b, 508 c, 508 d for supportingan alignment rod (not shown). In operation, the sliding alignment rodholder 500 slides substantially in the medial/lateral direction to allowthe alignment rods to be positioned adjacent the anterior tibia whenused in a unicondylar surgery of the medial or lateral compartment ofthe left or right knee. An advantage of the present embodiment of theknee joint instrument handle assembly and alignment rod holder is thatthe alignment rod can be placed directly anterior of the tibia, thuseliminating possible error such as parallax error, especially duringunicondylar knee surgery.

FIG. 8 illustrates an embodiment of a unicondylar femoral distalresection guide 600. The unicondylar femoral distal resection guide 600has a channel 602 to guide the path of a cutting instrument, such as asurgical saw. The unicondylar femoral distal resection guide 600 can beconfigured to be reversible, such that it can be used for either theright or left knee while the open side of the channel 602 always facesthe outside of the knee. The unicondylar femoral distal resection guide600 can also be provided with openings 604 a, 604 b for the passage of afixing element such as a fixation pin (not shown) to secure the cuttingblock to the distal femur. A pair of shoulders 606 a, 606 b arepositioned on the ends of the unicondylar femoral distal resection guide600 for sliding engagement with the slide tracks 404 a, 404 b of theinstrument handle assembly 400. The unicondylar femoral distal resectionguide 600 is symmetric about a horizontal plane H. In an alternativeembodiment the unicondylar femoral distal resection guide can beprovided with multiple channels for guiding a cutting instrument.

In operation, after a tibia has been prepared or resected, theinstrument handle assembly 400, alignment rod holder 500, andunicondylar femoral distal resection guide 600 are assembled andpositioned within the knee joint. A series of incrementally sized spacerblocks 408′ as shown in FIG. 9, are then used to evaluate flexion andextension space after the tibia resection is made. Spacer blockthicknesses are designed to represent the corresponding tibial implantthicknesses, which are typically incremented in whole millimeters, suchas 6, 7, 8, 9, and 10 mm. Fixation pins (not shown) are then used tosecure the unicondylar femoral resection guide 600 to the femur.

The knee joint instrument handle assembly 400 provides for easy removalfrom the knee joint even when the unicondylar femoral resection guide600 is fixed to the femur manually or with pins. The positioning of theopenings 604 a, 604 b in the unicondylar femoral resection guide 600allows for easy access for the saw while the fixation pins are in place.Moreover, the distal femoral resection can be advantageously made withor without the knee joint spacer block in place. The unicondylar femoraldistal resection guide 600 can be removeably connectable or slidinglyand removeably connectable to the base 406. The unicondylar femoraldistal resection guide 600 can be configured to operate concurrently andindependently with the spacer block 408.

A series of unicondylar femoral distal resection blocks 600′ is shown inFIG. 10. Each unicondylar femoral distal resection block 600 can beconfigured to have a different femoral resection depth D_(R) relative tothe superior surface of the base 406. Accordingly, the resection levelT, as shown in FIGS. 11 a and 11 b can be made with varying combinationsof spacer blocks 408′ and unicondylar femoral distal resection guides600′.

FIG. 13 illustrates a unicondylar femoral posterior resection guide 700.Similar to the unicondylar femoral distal resection guide 600, theunicondylar femoral posterior resection guide 700 has a channel 702 toguide the path of a cutting instrument. The unicondylar femoralposterior resection guide 700 can be configured to be reversible, suchthat it can be used for either a right or left knee while the open sideof the channel always faces the outside of the knee. The unicondylarfemoral posterior resection guide 700 can also be provided with openings704 a, 704 b, 704 c for the passage of fixation pins (not shown) tosecure the cutting block to the femur. A pair of shoulders 706 a, 706 bis positioned on the ends of the posterior resection guide for slidingengagement with the slide tracks 404 a, 404 b of the instrument handleassembly 400.

The unicondylar femoral posterior resection guide 700 can be provided asa series of unicondylar femoral posterior resection guides 700′ (FIG.14), similar to the series of unicondylar femoral distal resectionguides 600′. Likewise, each unicondylar femoral posterior resectionguide 700 can be configured to have a different posterior resectiondepth D_(R) relative to the superior surface of the base 406 (e.g., 4,5, 6, 7, 8, 9, and 10 mm). The resection level T for making a distalresection can be made with varying combinations of spacer blocks 408′and unicondylar femoral posterior resection guides 700′.

The present unicondylar knee instrument system allows for femoralresection depths to be determined based upon the knee joint pathology,i.e., the least affected or least damaged surface of the femoral knee.That is, if the distal surface of the femur is damaged (FIG. 11 a), itwould be desirable to reference off the posterior condyle to determinethe appropriate spacer block/resection guide combination to use.Alternatively if the posterior surface of the femur is damaged (FIG. 12b), it would be desirable to reference off the distal condyle todetermine the appropriate spacer block/resection guide combination touse.

For example, if the least affected site is the posterior condyle (FIG.11 b), the appropriate knee joint spacer block thickness needed to fillthe flexion space F would be determined with knee in flexion. Once theappropriate spacer block thickness is determined, for example a 10 mmspacer block, then the overall thickness T can be determined taking intoaccount the implant thickness, for example a 5 mm thick implant (i.e., a5 mm resection guide is necessary). The appropriate spacer blockthickness is one that properly balances the knee (i.e., collateralligaments are not too tight or too loose). Thus, the proper spacerblock/resection guide combination can be one that provides for anoverall thickness T of 15 mm. Thereafter, the extension space E can befilled with an appropriate spacer block 400, (most likely a largerthickness than that necessary to fill the flexion space) and theappropriate distal resection guide can be selected to provide for anoverall thickness of 15 mm. That is, if the necessary spacer block tofill the extension space E is 12 mm, then the appropriate distalresection guide would be 3 mm. Thus, the present unicondylar kneeinstrument system allows the user to compensate for diseased or damagedsurfaces of the bone by choosing different size spacer blocks 408′ andunicondylar femoral resection guides 700′ and initially referencing offthe least affected region of the femur (either distal or posterior) toprovide for the most accurate restoration of the anatomic joint line.

Regardless of whether the distal femur is damaged or not, the distalresection is made first. Making the distal resection first allows for amuch better angular reference surface to make the posterior resectionlater in the surgery.

An advantage of the present system is that the instrumented techniquereduces the need for up-sizing or down-sizing the implant size as thebone resection and knee balancing steps are concurrently conducted. Thatis, the resection guides are used concurrently with the balancing andalignment instruments. This allows for greater accuracy in femoralresections and in balancing the knee joint, compared to conventionalsystems that make separate tibial and femoral resections that are notreferenced off of each other. The present system also advantageouslyallows for determining the proper resection depth based upon the leastaffected condyle and then assembling the necessary combination of spacerblock and resection block to provide the appropriate resection depth.

FIG. 15 illustrates an embodiment of a unicondylar femoral chamfer andpeg-hole guide 800. The guide 800 can align a femoral chamfer cut on thedistal femur and guides the drilling of peg holes for implanting aunicondylar femoral implant having pegs. The guide 800 can be L-shapedhaving a distal end 802 and a posterior end 804. The distal end 802 hastwo openings 806, 808 and a flange opening 810, for guiding a cuttinginstrument, such as a surgical drill, for making peg holes. The positionof the openings 806, 808, 810 correspond to the position of peg holes ona corresponding unicondylar femoral knee implant having pegs. The distalend has an additional opening 812 for accepting a fixation pin (notshown) to secure the guide 800 to the distal femur. The opening 812 canbe oriented to allow for easy saw and drill access when the fixation pinis in place. The unicondylar femoral chamfer and peg-hole guide 800 canalso be configured to have multiple openings for accepting multiplefixation pins. A chamfer resection guide slot 814 extends from thedistal end 802 to the posterior end 804 to guide a cutting instrument inmaking a chamfer cut on the distal femur to closely match that of aunicondylar femoral knee implant having a chamfer bone engaging surface.

In operation, a chamfer resection can be made using the chamferresection guide slot 810 and a cutting instrument, such as a sagittalsaw. The peg holes are made by using the peg-hole guides 806, 808, 810and a cutting instrument, such as a step drill. The unicondylar femoralchamfer and peg-hole guide 800 can be fixed to the femur with at leastone fixation pin.

The chamfer and peg-hole guide 800 can also be used to size the femurand to determine the medial lateral position of the definitive implant.The distal and posterior resections are not size dependent thus, theuser does not need to determine implant sizing until the last femoralresections are made i.e., femoral chamfer resection. The femoral chamfercut is the only implant size dependent resection. The distal profile 816closely matches the distal profile of the definitive implant to allowfor proper sizing and medial/lateral positioning based upon fit and bonecoverage. The posterior profile 818 also closely matches that of thedefinitive implant so that a check for overhang and coverage can bemade. The unicondylar chamfer and peg hole guide can also be provided asa series of chamfer and peg hole guides 800′, as shown in FIG. 16,similar to the series of unicondylar femoral distal resection guides600′. Likewise, each chamfer and peg hole guide can be configured tomatch the resection levels of the corresponding unicondylar femoraldistal 600′ and unicondylar femoral posterior 700′ resection guides.

The present unicondylar knee instrument system also provides for amethod of preparing a femoral condyle of a knee for the implantation ofa unicondylar femoral knee implant (as shown in FIG. 17) that includesthe steps of resecting a tibia (Step 900), determining a least affectedsite (Step 902), wherein the site is a distal femoral condyle or aposterior femoral condyle, positioning the knee such that the leastaffected site faces the tibia (Step 904), positioning a spacer blockbetween the resected tibia and the least affected site (Step 906). Thenthe step of determining an overall thickness for balancing the knee andresecting the femur to a thickness of a corresponding unicondylarfemoral implant (Step 908), determining a spacer block and femoralcutting block combination that equals the overall thickness when theknee is in extension (Step 910), and resecting the distal femoralcondyle (Step 912).

The embodiments of the present unicondylar knee instrument system areshown and described for purposes of illustration only and not forpurposes of limitation. While there have been shown, described, andpointed out fundamental novel features of the invention as applied toseveral embodiments, it will be understood that various omissions,substitutions, and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit and scope of the invention.Substitutions of elements from one embodiment to another are also fullyintended and contemplated. It is also to be understood that the drawingsare not necessarily drawn to scale, but that they are merely conceptualin nature. The invention is defined solely with regard to the claimsappended hereto, and equivalents of the recitations therein.

The above mentioned patents, applications, and publications are herebyincorporated by reference in their entirety.

1-8. (canceled)
 9. A tibial stylus for use in support of a unicondylarknee surgery comprising: a tibial stylus pointer; a member having anopen top surface; and a tibial stylus base having: a posterior endconfigured to slidingly engage along the open top surface; and anelongated anterior end connectable to the tibial stylus, configured suchthat the tibial stylus pointer moves along the anterior end of thetibial stylus base.
 10. The tibial stylus of claim 9, wherein the memberis a unicondylar tibial resection guide comprising: an extended armhaving at least one cutting surface; and a tibial resection guide baseconnected to the extended arm.
 11. The tibial stylus of claim 9, whereinthe posterior end of the tibial stylus base is U-shaped.
 12. Anapparatus for cutting a femur in support of a unicondylar knee surgerycomprising: an instrument handle assembly including: an elongated handlehaving a base; and a spacer block removably connectable to the base; anda unicondylar resection guide removably connectable to the base andconfigured to operate concurrently with the spacer block including: atleast one channel for guiding a cutting tool; and at least one openingfor receiving a fixing element.
 13. The apparatus of claim 12, whereinthe unicondylar resection guide is slidingly and removably connectableto the base.
 14. The apparatus of claim 12, wherein the spacer block andunicondylar resection guide are configured to operate independently ofeach other.
 15. An apparatus for aligning a unicondylar femoralresection guide in support of a unicondylar knee surgery comprising: aninstrument handle assembly having a base; and an alignment rod holderconnected to the instrument handle assembly that slides substantially inthe medial and lateral direction.
 16. The apparatus of claim 15, furthercomprising a unicondylar resection guide removably connectable to thebase.
 17. The apparatus of claim 15, further comprising a unicondylarresection guide slidingly and removably connectable to the base.
 18. Theapparatus of claim 15, further comprising a spacer block removablyconnectable to the base.
 19. The apparatus of claim 15, wherein thealignment rod holder comprises: a first alignment rod holder base havingat least one substantially vertical passage; a second alignment rodholder base having at least one substantially vertical passage; and atleast one dowel connecting the first and second alignment rod holderbases such that the first and second alignment rod holder bases slidewithin the instrument handle assembly in a substantially medial andlateral direction.
 20. An ankle clamp for supporting an apparatus forcutting a tibia in support of a unicondylar knee surgery, comprising: anankle clamp base that includes a pair of base arms, each having a slot;a pair of clamping arms, each having a slot and pivotably connected tothe pair of base arms; and a pair of springs, each respectivelyconnecting the base arm and the clamping arm such that an opening forceis provided to open the clamping arm.
 21. The ankle clamp of claim 20,wherein the pair of springs, each respectively connecting the base armand the clamping arm, provides a clamping force to close the clampingarm.
 22. The ankle clamp of claim 20, wherein each one of the pair ofsprings are connected to a dowel, offset a predetermined distance fromthe pivotable connection of the clamping arms and base arms.
 23. Theankle clamp of claim 20 further comprising a tibial alignment guideconnected to the ankle clamp base.
 24. A method of preparing a femoralcondyle of a femur for the implantation of a unicondylar femoral kneeimplant comprising the steps of: resecting a tibia; determining a leastaffected site, wherein the site is a distal femoral condyle or aposterior femoral condyle; positioning the knee such that the leastaffected site faces the tibia; positioning a spacer block between theresected tibia and the least affected site; determining an overallthickness for balancing the knee and resecting the femur to a thicknessof a corresponding unicondylar femoral implant; determining a spacerblock and unicondylar femoral cutting block combination that equals theoverall thickness when the knee is in extension; and resecting thedistal femoral condyle.